BRUSSELS
— The G-8 summit this weekend in St. Petersburg, Russia, was supposed to provide an opportunity for eight of the world's top leaders to discuss energy security, world trade liberalization, and global health and education.

Those topics will still come up, but Iran, North Korea, and the Middle East are clamoring for attention, like uninvited guests at the gates of a sumptuous banquet.

The mere fact that two smaller countries' nuclear ambitions, as well as the escalation of Mideast violence, are likely to dominate this meeting is an indication of how these summits have changed – from economics-focused discussions, to increasingly political gatherings where diversifying viewpoints have made bold action increasingly difficult.

"Sometimes on economic summits, the economic issues get the main billing because consensus is approaching and you can bring things to closure. And sometimes when that is not the case, as is the case this year, the politics tend to get a higher billing," Richard McCormack, a former undersecretary of State for economic affairs, told a Washington gathering recently.

Among the areas of economic discord that Ambassador McCormack cites are the Doha round of global trade liberalization negotiations, a disconnect between America's need to address its current account deficit and the developing world's "desperate need" to increase exports, and tension over energy interests in Iran.

Others say the G-8 is simply reflecting diversifying national interests, in a world no longer polarized along East-West lines.

"What we're seeing is the G-8 going with the times," says Constanze Stelzenmüller, a transatlantic security expert who heads the German Marshall Fund's Berlin office. "We now have fissures among the partners, even values differences that are increasingly pronounced, when before the overarching issue [of the cold-war divide] was so much larger that political differences didn't stand out."

Russia's accession to the big-boy club is another factor in the loss of easier consensus. That is especially true at a time when President Vladimir Putin appears to act in an increasingly authoritarian manner toward Russian civil society and some neighbors of the former Soviet Union.

Some experts believe that Mr. Putin is actually out to challenge American leadership with a more controlling, centralized, and less transparent example of government. "I'm not sure we can cooperate that effectively with Russia," says Joshua Muravchik, an expert in international institutions at the American Enterprise Institute (AEI) in Washington. "At some point, we have to take into account that Russia under Putin is not just aiming to develop its own idea of democracy, but really to counterbalance us."

Indeed, as summit host, Putin intends to showcase a wealthier and more assertive Russia, one he touts as an "energy superpower." And as the one who sets the agenda, Putin has wanted the discussions to focus on energy security – a topic that harks back to earlier summits in the 1970s and '80s, when the group was seven Western democracies against the world's major oil producers. From those deliberations came the International Energy Agency, strategic oil reserves, and arrangements for helping fellow club members with energy supplies in times of disaster.

Yet while oil experts think more global attention to a new generation of energy security arrangements is essential, few of them seem to expect major action.

For one thing, interests vary. Russia is an oil and natural-gas supplier, and it has been opposed to the kind of system transparency and investment freedom and guarantees that consumers in the group, including the United States, want to see.

Indeed, the hurdles to reaching meaningful agreement on energy security seem so high that the weekend's main events could occur even before the eight leaders get down to business, when President Bush meets Putin Saturday.

Officials from both countries are talking with increased optimism about the US reaching a trade agreement with Russia that would pave the way for it to join the World Trade Organization. At the same time, the US is expected to announce a White House decision to begin negotiating a civilian nuclear cooperation agreement with Russia.

Such an agreement could result in tighter security for Russia's nuclear materials and weapons-of-mass-destruction stocks, some experts say. But as proposed, it also includes a provision to make Russia a repository for the nuclear waste of countries with American-built nuclear power plants, including South Korea and Japan.

Such an arrangement would be extremely lucrative for Russia. But it also has some human rights experts worried that it would be "the last nail in the coffin of George Bush's concern about Russia's deteriorating democracy," as one such expert says, while insisting on anonymity because of ongoing work with both governments.

But other analysts say this "carrot" that the White House is dangling is really more about Iran, and winning Russia's support for a tougher stance toward Tehran's nuclear ambitions. "The administration has concluded that by beginning negotiations, the agreement could be a source of continuing leverage over the Russians" as the international community continues to confront the Iranians, says Robert Einhorn, nonproliferation and security expert at the Center for Strategic and International Studies in Washington.

Mr. Einhorn says the prospects for a Russia deal, taken together with the civilian nuclear agreement the White House wants to conclude with India, could form the basis of a new nuclear security architecture for a world of galloping energy needs. "The common thread behind this is a world relying more all the time on nuclear energy," he says.

The multifaceted reasoning behind offering Russia a nuclear agreement also serves as an example for some diplomatic realists of why a country like Russia needs to be in an organization like the G-8. Supporters of that view say that in fact, the G-8 should be expanded to take in China and India.

But not everyone agrees. "It's already unfortunate to have Russia in the G-8," says Mr. Muravchik of AEI. "Add China and a few others, and you'd end up manufacturing molasses. You wouldn't get anything done."